Semiconductor device

ABSTRACT

Power amplifier circuits which constitute an RF power module used for a digital device capable of handling high frequency signals in two frequency bands are disposed over the same IC chip. The power amplifier circuits are disposed around the IC chip, and a secondary circuit is disposed between the power amplifier circuits. Thus, the power amplifier circuits are provided within the same IC chip to enable a size reduction. Further, the distance between the power amplifier circuits is ensured even if the power amplifier circuits are provided within the same IC chip. It is therefore possible to suppress the coupling between the power amplifier circuits and restrain crosstalk between the power amplifier circuits.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority to Japanese Patent applicationJP 2003-290136 filed on Aug. 8, 2003, the content of which is herebyincorporated by reference in its entirety herein.

FIELD OF THE INVENTION

The present invention relates to a semiconductor device and method, and,more particularly, to a device, system, and method for an RF (RadioFrequency) power module.

BACKGROUND OF THE INVENTION

An RF power module is a signal amplifying electronic component used in acommunication device such as, for example, a cellular phone, or thelike. The RF power module is assembled by packaging semiconductor chips,each having signal amplifying transistors, chip parts, and the like,over a module board. The respective semiconductor chips and the moduleboard are electrically connected to one another through bonding wires.Also, the chip parts can be electrically connected to the module boardby connecting their terminals to pads of the module board by soldering.

Such a configuration with a bias circuit and a bias switch circuitemployed in high frequency power amplifiers for a dual band systemconstructed of HBTs (Heterojunction Bipolar Transistors), has beendisclosed in Japanese Patent Laid-Open No. 2000-332551.

Further, such a configuration that, in high frequency parts orcomponents for a dual band system, includes a plurality of GND linesprovided between output microstrip lines to prevent interference betweentwo outputs has been disclosed in, for example, Japanese PatentLaid-Open No. 2001-141756.

Furthermore, a technique for providing ground pads between output padsof both a semiconductor chip and a wiring board to prevent interferencebetween two outputs in a power module for a dual band, and forwire-bonding, has been disclosed in, for example, Japanese PatentLaid-Open No. 2001-345400.

SUMMARY OF THE INVENTION

The miniaturization of the RF power module has been provided herein. Animportant problem exists in how to miniaturize the RF power modulewithout causing degradation of characteristics like reliability,performance, etc.

The present invention may provide a technique for decreasing the size ofa semiconductor device.

The present invention may provide a semiconductor device wherein all ofa plurality of stages of amplifier circuits of high frequency poweramplifier circuits may be respectively formed of horizontal type fieldeffect transistors and may be provided over the same semiconductor chiphaving a silicon semiconductor substrate.

Since all of a plurality of stages of amplifier circuits of highfrequency power amplifier circuits may be respectively formed ofhorizontal type field effect transistors and may be provided over thesame semiconductor chip having a silicon semiconductor substrate, asemiconductor device may be reduced in size.

BRIEF DESCRIPTION OF THE DRAWINGS

Understanding of the present invention will be facilitated byconsideration of the following detailed description of the preferredembodiments of the present invention taken in conjunction with theaccompanying drawings, in which like numerals refer to like parts, andwherein:

FIG. 1 is a circuit block diagram showing a semiconductor deviceaccording to an exemplary embodiment of the present invention;

FIG. 2 is a fragmentary circuit diagram illustrating the semiconductordevice shown in FIG. 1;

FIG. 3 is an overall plan view of a semiconductor chip, showing acircuit layout example of the semiconductor device shown in FIG. 1;

FIG. 4 is a graph diagram depicting the relationship between a distanceand a power leak;

FIG. 5 is a fragmentary plan view showing the semiconductor chip of thesemiconductor device shown in FIG. 1;

FIG. 6 is a fragmentary cross-sectional view illustrating thesemiconductor chip shown in FIG. 5;

FIG. 7 is a circuit diagram showing an equivalent circuit of anamplifying stage of the semiconductor chip shown in FIG. 5;

FIG. 8 is an overall plan view illustrating one example of an RF powermodule in which the semiconductor chip shown in FIG. 5 is mounted on amodule board;

FIG. 9 is a cross-sectional view showing the RF power module shown inFIG. 8;

FIG. 10 is a circuit diagram illustrating an equivalent circuit of theRF power module shown in FIG. 8;

FIG. 11 is an explanatory view showing one example of a digital cellularphone system using the RF power module shown in FIG. 8;

FIG. 12 is a fragmentary side view illustrating a packaged example ofthe RF power module of the digital cellular phone system shown in FIG.11;

FIG. 13 is an overall plan view of a semiconductor chip, showing acircuit layout example of a semiconductor device according to anotherexemplary embodiment of the present invention;

FIG. 14 is an overall plan view illustrating one example of an RF powermodule in which the semiconductor chip shown in FIG. 13 is mounted on amodule board;

FIG. 15 is an overall plan view of a semiconductor chip, showing acircuit layout example of a semiconductor device according to a furtherexemplary embodiment of the present invention;

FIG. 16 is an overall plan view illustrating one example of an RF powermodule in which the semiconductor chip shown in FIG. 15 is mounted on amodule board; and

FIG. 17 is an overall plan view of a semiconductor chip, showing acircuit layout example of a semiconductor device according to yetanother exemplary embodiment of the present invention.

DETAILED DESCRIPTION

It is to be understood that the figures and descriptions of the presentinvention have been simplified to illustrate elements that are relevantfor a clear understanding of the present invention, while eliminating,for the purpose of clarity, many other elements found in typicalsemiconductor devices, systems and methods. Those of ordinary skill inthe art may recognize that other elements and/or steps are desirableand/or required in implementing the present invention. However, becausesuch elements and steps are well known in the art, and because they donot facilitate a better understanding of the present invention, adiscussion of such elements and steps is not provided herein. Thedisclosure herein is directed to all such variations and modificationsto such elements and methods known to those skilled in the art.

Prior to the detailed description of embodiments of the presentinvention, the meaning of certain terms employed in embodimentsdiscussed hereinbelow is explained as follows:

1. GSM (Global System for Mobile Communication) may indicate onewireless communication system or standard used in a digital cellularphone. GSM may include three frequency bands of a radio wave, such as a900 MHz band called “GSM900” or simply “GSM”, a 1800 MHz band called“GSM1800” or “DCS1800” (Digital Cellular System) or PCN, and 1900 MHzband called “GSM1900”, “DCS1900”, or “PCS” (Personal CommunicationServices). Incidentally, GSM1900 may be principally used in NorthAmerica. In addition, GSM850, corresponding to an 850 MHz band, mightalso be used in North America.

2. A GMSK (Gaussian filtered Minimum Shift Keying) modulation system orscheme may be a system used in communications of audible or voicesignals, i.e., a system that phase-shifts the phase of a carrieraccording to transmit data. An EDGE modulation system or scheme may be asystem used in data communications, i.e., a system in which an amplitudeshift may be further added to a phase shift of GMSK modulation.

3. A MOSFET (Metal Oxide Semiconductor Field Effect Transistor),corresponding to a field effect transistor, may be abbreviated as “MOS”,and an n channel type MOS may be abbreviated as “nMOS”.

In an exemplary embodiment of the present invention, a semiconductordevice may be applied to an RF (Radio Frequency) power module used in adigital cellular phone for transmitting information by using, forexample, a network of a GMS system.

As shown in FIG. 1, a circuit block diagram of an IC (integratedcircuit) chip (or semiconductor chip) 1C for amplifier circuits, whichmay constitute an RF power module according to the present embodiment,is illustrated. A circuit block of an 1C chip (semiconductor chip) 1Cfor amplifier circuits, which may be used in the RF power module capableof using two frequency bands (dual band system) of, for example, GSM900and DCS1800, and using two communication systems of the GMSK modulationsystem and the EDGE (Enhanced Data GSM Environment) modulation system attheir frequency bands, is illustrated in FIG. 1.

The IC chip 1C may include a power amplifier circuit 2A for GSM900, apower amplifier circuit 2B for DCS1800, and a peripheral circuit 3 whichmay effect control, compensation and the like on amplifying operationsof the those power amplifier circuits 2A and 2B. The power amplifiercircuits 2A and 2B respectively may have three amplifying stages 2A1through 2A3 and 2B1 through 2B3 and three matching circuits 2AM1 through2AM3 and 2BM1 through 2BM3. That is, input terminals 4 a and 4 b of theIC chip 1C may be electrically connected to their corresponding inputsof the amplifying stages 2A1 and 2B1, each corresponding to a firststage via the input matching circuits 2AM1 and 2BM1. The outputs of theamplifying stages 2A1 and 2B1, each corresponding to the first stage,may be electrically connected to their corresponding inputs of theamplifying stages 2A2 and 2B2, each corresponding to a second stage viathe inter-stage matching circuits 2AM2 and 2BM2. The outputs of theamplifying stages 2A2 and 2B2 may be electrically connected to theircorresponding inputs of the final-stage amplifying stages 2A3 and 2B3via the inter-stage matching circuits 2AM3 and 2BM3. The outputs of thefinal-stage amplifying stages 2A3 and 2B3 may be electrically connectedto their corresponding output terminals 5 a and 5 b. Thus, in thepresent exemplary embodiment, all the amplifying stages 2A1 through 2A3and 2B1 through 2B3 of the power amplifier circuits 2A and 2B may beprovided in one IC chip 1C. In general, three amplifying stages may berespectively provided in discrete IC chips, or the amplifying stagescorresponding to the first and second stages may be provided in one ICchip and the final-stage amplifying stage may be provided in an IC chipdifferent from the IC chip provided with the first-stage andsecond-stage amplifying stages, because, for example, the power of thefinal-stage amplifying stage may be high and generated heat may increaseupon its operation, and thus signal interference with other amplifyingstages may also increase. Therefore, miniaturization of the RF powermodule may be impaired. On the other hand, since all the amplifyingstages 2A1 through 2A3 and 2B1 through 2B3 of the power amplifyingstates 2A and 2B may be provided in one IC chip 1C in the presentexemplary embodiment, the adjacent intervals among the respectiveamplifying stages 2A1 through 2A3 and 2B1 through 2B3 may be greatlyshortened. It may therefore be possible to realize substantialminiaturization of the RF power module with the IC chip 1C builttherein.

The peripheral circuit 3 may include a control circuit 3A, and a biascircuit 3B, which may apply a bias voltage to each of the amplifyingstages 2A1 through 2A3 and 2B1 through 2B3, etc. The control circuit 3Amay be a circuit which may generate a desired voltage to be applied toeach of the power amplifier circuits 2A and 2B and may include a powersupply control circuit 3A1 and a bias voltage generating circuit 3A2.The power supply control circuit 3A1 may be a circuit which generates afirst power supply voltage applied to each of drain terminals of outputpower MOSs of the amplifying stages 2A1 through 2A3 and 2B1 through 2B3.Also, the bias voltage generating circuit 3A2 may be a circuit which maygenerate a first control voltage for controlling the bias circuit 3B.The present exemplary embodiment may be configured in such a manner thatwhen the power supply control circuit 3A1 generates the first powersupply voltage, based on an output level designation signal suppliedfrom a baseband circuit provided outside the IC chip 1C, the biasvoltage generating circuit 3A2 may generate the first control voltage,based on the first power supply voltage generated by the power supplycontrol circuit 3A1. The baseband circuit may be a circuit whichgenerates the output level designation signal. The output leveldesignation signal may be a signal for designating or specifying outputlevels of the power amplifier circuits 2A and 2B and may be generatedbased on the distance between a cellular phone and a base station, i.e.,an output level corresponding to the intensity of a radio wave. In thepresent exemplary embodiment, elements constitutive of such a peripheralcircuit 3 may also be provided in one IC chip 1C. Thus, interface units(interface unit between IC chip 1C and module board (wiring board) andinterface units, respectively, necessary for IC chip 1C and moduleboard) may be greatly cut down, and the IC chip 1C and the module boardmay be reduced in area. It may therefore be possible to realizesubstantial miniaturization of the RF power module.

As seen in FIG. 2, an example illustrative of circuit configurations ofthe power amplifier circuit 2A and the bias circuit 3B is shown.Incidentally, since the power amplifier circuits 2A and 2B and theirbias circuit 3B may be identical in circuit configuration, the poweramplifier circuit 2A and an example of the circuit configuration for thepower amplifier circuit 2A may be shown as representative of the presentembodiment.

The power amplifier circuit 2A according to the present embodiment 1 mayhave a circuit configuration wherein three nMOSQn (Qn1, Qn2 and Qn3) maybe sequentially connected in tandem as the three-stage amplifying stages2A1 through 2A3. The output level of the power amplifier circuit 2A maybe controlled by the bias circuit 3B and the first power supply voltageVdd1 supplied from the power supply circuit 3A1. In the presentembodiment, the first power supply voltage Vdd1 may be supplied to therespective drain electrodes of the three nMOSQn1, Qn2 and Qn3.

Each of the matching circuits 2AM1 through 2AM3 may have an inductor(passive element) and a capacitor (passive element). The inductor may beformed of a wiring and may have the function of impedance-matchingbetween the input of the amplifying stage 2A1 (nMOSQn1), correspondingto the first stage, and each of the respective interstages. Thecapacitor may be connected between the inductor and each of the inputsof the nMOSQn of the respective stages and may additionally have thefunctions of the impedance matching, and that of shutting off dcvoltages of the first power supply voltage Vdd1 and a gate bias voltage.

The bias circuit 3B may have a plurality of voltage division circuits.Each of the voltage division circuits may include a pair of resistors R1and R2. Each pair of resistors R1 and R2 may be connected in seriesbetween an input terminal 4 c of the bias circuit 3B and a referencepotential (e.g., ground potential: 0V). Wiring portions that connectamong the respective pairs of resistors R1 and R2 and the inputs (gateelectrodes) of the nMOSQn1 through Qn3 of the respective stages may beelectrically connected to one another, respectively. When the firstcontrol voltage or output level control voltage is inputted to the inputterminal 4 c of the bias circuit 3B, the voltage may be divided by eachpair of resistors R1 and R2 to thereby generate a desired gate biasvoltage, which in turn may be inputted to each of the gate electrodes ofthe respective nMOSQn1 through Qn3.

As seen in FIG. 3, an example of a circuit layout of the IC chip 1C forthe amplifier circuits, which is shown in FIG. 1, is shown.Additionally, FIG. 4 shows a graph diagram illustrating the relationshipbetween a distance and a power leak, respectively.

In the present exemplary embodiment as is shown in FIG. 3, the poweramplifier circuits 2A and 2B may be disposed around a main surface(device forming surface) of the IC chip 1C, and the peripheral circuit 3may be disposed between the respective power amplifier circuits 2A and2B. Since the final-stage amplifying stages 2A3 and 2B3 of the poweramplifier circuits 2A and 2B may be high in power, an increase in heatgenerated upon their operation may cause an increase in signalinterference with other amplifying stages. Problems with interferencebetween signals may be large because the phases of respective higherharmonics may be inverse, such as in the case where high frequencysignals to be treated may be 900 MHz and 1800 MHz, respectively. Asdescribed above, the final-stage amplifying stages 2A3 and 2B3 may bedisposed in the vicinity of opposed sides of the IC chip 1C, such thatthe distance therebetween may become long. Since the amount ofpropagation of a signal between two points may be inversely proportionalsubstantially to the square of the distance, as shown in FIG. 4, thepower amplifier circuits 2A and 2B may be disposed away from each otheras described above, whereby crosstalk (radiation or interference)between the power amplifier circuit in operation and the power amplifiercircuit in non-operation, for example, may be suppressed. Further, theoccurrence of an unnecessary output from the power amplifier circuitbeing in non-operation may be suppressed. Even if the power amplifiercircuits 2A and 2B, which may be different in a system, are provided inthe same IC chip 1C, the crossband isolation characteristic between thepower amplifier circuits 2A and 2B may be improved. It may thus bepossible to enhance reliability and stability of the operation of the RFpower module.

Signs Pin in FIG. 3 may indicate input bonding pads and signs Pout mayindicate output bonding pads, respectively. The bonding pads Pin of therespective amplifying stages 2A1 through 2A3 and amplifying stages 2B1through 2B3 may be placed over the central side of the IC chip 1C,whereas the bonding pads Pout of the respective amplifying stages 2A1through 2A3 and the amplifying stages 2B1 through 2B3 may be disposed onthe sides of the IC chip 1C. Signs M may indicate input, output andamplifying interstage wirings, respectively. The amplifying interstagewirings M may connect between the bonding pads Pin and Pout in bentstates. Further, signs M may indicate wirings which connect theamplifying stages 2A1 through 2A3 and 2B1 through 2B3 and the peripheralcircuit 3.

As seen in FIG. 5, a fragmentary plan view of the IC chip 1C is shown.Additionally, FIG. 6 shows a fragmentary crosssectional view of a spotcut along the horizontal direction of the CI chip 1C shown in FIG. 5.Incidentally, although FIG. 5 is a plan view, the same hatching may beapplied to ones lying in the same layer.

A semiconductor substrate (hereinafter also “substrate”) 1S,constituting the IC chip 1C, may include, for example, a p⁺ type silicon(Si) monocrystal and may be configured as a low resistance substratewhose resistivity ranges from, for example, approximately 1 to 10 mΩ·cm.An epitaxial layer 1EP comprising, for example, a p⁻ type siliconmonocrystal may be formed over the substrate 1S. The resistivity of theepitaxial layer 1EP may be higher than that of the substrate 1S. Over amain surface of the epitaxial layer 1EP, nMOSQn for the amplifyingstages 2A1 through 2A3 and 2B1 through 2B3, and inductors L1, capacitorsC1 each having a high Q (Quality factor) value and strip lines for thematching circuits 2AM1 though 2AM3 and 2BM1 through 2BM3, may be formed.Although the nMOSQn1 and Qn2 of the two amplifying stages areillustrated in the present embodiment, the amplifying stages 2A1 through2A3 and 2B1 through 2B3 of all of the first through three stages may beformed over the same substrate 1S as described above. The nMOSQn shownhere indicate unit MOSs. In practice, a plurality of the unit MOSs maybe connected in parallel to form the respective one of the amplifyingstages 2A1 through 2A3 and 2B1 through 2B3.

First, the nMOSQn may be formed of a horizontal type MOS like, forexample, an LDMOS (Laterally Diffuses MOS), or the like. A type well PWLmay be formed in the epitaxial layer 1EP, corresponding to a region forforming each nMOSQn. The p type well PWL may be formed by ion-implantingan impurity, such as boron (B), into the epitaxial layer 1EP. A gateinsulating film 7 for each nMOSQn may be formed over the p type well PWLof the epitaxial layer 1E P. The gate insulating film 7 may be formedof, for example, silicon oxide (SiO₂), or the like, and may further beformed by, for example, a thermal oxidation method, or the like. A gateelectrode (input) 8 for each nMOSQn may be formed over the gateinsulating film 7. The gate electrode 8 may include a laminatedconductor film of, for example, polycrystalline silicon, and a metalsilicide layer (e.g., titanium silicide layer or cobalt silicide layer)formed thereon. A channel for each nMOSQn may be formed above the p typewell PWL located below the gate electrode 8.

An n⁺ type semiconductor region 9 may be formed within a region for thep type well PWL, which may be located in the vicinity of one end of eachgate electrode 8. The n⁺ type semiconductor region 9 may be a regionwhich functions as the source of the nMOSQn and may be formed byion-implanting an impurity, such as phosphorous (P), into the p typewell PWL. An n type semiconductor region 10 a may be formed in theepitaxial layer 1EP in the vicinity of the other end of the gateelectrode 8. Then, an n⁺ type semiconductor region 10 b may be formed ata spot spaced by the n⁻ type semiconductor region 10 a from the otherend of the gate electrode 8, being electrically connected to the n⁻ typesemiconductor region 10 a (LDD (Lightly Doped Drain) structure). The ntype semiconductor region 10 a and the n⁺ type semiconductor region 10 bmay be regions which function as the drains (outputs) of the nMOSQn andmay be formed by ion-implanting an impurity, such as phosphorous (P),into the corresponding p type well PWL.

In the present exemplary embodiment, p⁺⁺ type semiconductor regions 11 amay be formed in the epitaxial layer 1EP for the region for forming eachnMOSQn so as to make contact with the n⁺ type semiconductor regions 9and 10. The p⁺⁺ type semiconductor regions 11 a may be provided byintroducing, for example, boron (B), and may be formed so as to surroundeach nMOSQn as viewed in its plane and formed so as to extend from themain surface of the epitaxial layer 1EP to the substrate 1S, as viewedin its section. In the present embodiment, the n⁺ type semiconductorregion 9 for the source of each nMOSQn may be electrically connected toits corresponding p⁺⁺ type semiconductor region 11 a through a plug PL1and electrically connected to the low resistance p⁺ type substrate 1Sthrough the p⁺⁺ type semiconductor region 11 a. As will be describedlater, the substrate 1S may be electrically connected to wirings of amodule board with the IC chip 1C packaged thereon, through an electrode12 formed over the whole back surface of the substrate 1S andelectrically connected to a reference potential (e.g., ground potentialGND, that is 0V: fixed potential) through the wirings. That is, thesubstrate 1S may be used as a ground portion common to the plurality ofnMOSQn formed in the IC chip 1C.

An equivalent circuit illustrative of this is seen in FIG. 7, wherenMOSQn1 and Qn2 of two amplifying stages 2A1 and 2A2 (or amplifyingstages 2B1 and 2B2) of the same power amplifier circuit 2A (or poweramplifier circuit 2B) are shown. Signs G1 and G2 may indicate gateelectrodes 8 of the MOSQn1 and Qn2. Since sources S1 and S2 (eachcorresponding to the n⁺ type semiconductor region 9) of the two nMOSQn1and Qn2 may be electrically connected to a ground potential GND via thep⁺⁺ type semiconductor regions 11 a and the p⁺ type substrate 1S, thepower amplifier circuit may have resistive components R11 and R21 of thep⁺⁺ type semiconductor regions 11 a and resistive components R12, R22and R3 of the p⁺ type substrate 1S. Since the resistivity of a substratefor the normal CMOS·LSI (Complementary MOS·Large Scale Integratedcircuit) may be high, such as multiples of 10 Ωcm, the resistivecomponents R11, R21, R12, R22 and R3 may become high if such aconfiguration as described in the present embodiment 1 is taken, andsignal gain of the source S1 of the nMOSQn1 with respect to the sourceS2 of the nMOSQn2 may be produced. Therefore, interference may occurbetween the nMOSQn1 and Qn2, oscillations and a gain reduction mayoccur, resulting in degradation of input/output isolation. On the otherhand, since the resistance of the substrate 1S may be low in the presentembodiment, the resistive components R21, R22 and R3 may be broughtclose to zero (0). In other words, the sources S1 and S2 of the twonMOSQn1 and Qn2 may become equivalent to the fact that they are bothdirectly connected to a stable ground. It may therefore be possible toavoid occurrence of interference between connected elements in thesubstrate 1S. For example, crosstalk between each of nMOSQn3 of thefinal-stage amplifying stages 2A3 and 2B3 and each of the amplifyingstages 2A1, 2A2, 2B1 and 2B2 corresponding to the first and secondstages and the peripheral circuit 3 may be reduced. That is, since thecharacteristics of isolation among the nMOSQn1 through Qn3 of therespective amplifying stages 2A1 through 2A3 and 2B1 through 2B3 may beimproved, oscillations may be suppressed and the stability of amplifyingcharacteristics of the nMOSQn1 through Qn3 may be enhanced. This meansthat similar isolation characteristics may be obtained not only amongthe amplifying stages 2A1 through 2A3 and 2B1 through 2B3 but also amongother circuit elements, and crosstalk between the circuit elements maybe reduced.

Included in the present invention are connections among the nMOSQn1 andQn2, inductors L1 and capacitors C1, as shown in FIGS. 5 and 6. The plugPL1 connected to the n⁺ type semiconductor region 9 for the source ofthe pre-stage nMOSQn1 may be electrically connected to its correspondingfirst layer wiring M11. The gate electrode 8 of the nMOSQn1 may beelectrically connected to its corresponding second layer wiring M21 (M)via a plug PL2 and a first layer wiring M12 (M). The second layer wiringM21 may be a wiring for the input of the nMOSQn1. The n⁺ typesemiconductor region 11 for the drain of the nMOSQn1 may be electricallyconnected to its corresponding first layer wiring M13 (M) via a plugPL3. The first layer wiring M13 may be electrically connected to one endof its corresponding inductor L1.

The inductor L1 may be formed of, for example, a spiral second layerwiring M22 The outer periphery of the inductor L1 may be surrounded by afirst layer wiring M14, a second layer wiring M23, plugs PL4 and p⁺⁺type semiconductor regions 11 b for shielding. The first layer wiringM14, the second layer wiring M23, the plugs PL4 and the p⁺⁺ typesemiconductor regions 11 b may be electrically connected to one another(insulated from the inductor L1). Further, they may be electricallyconnected to the low resistance substrate 1S via the p⁺⁺ typesemiconductor regions 11 b and may be set to the ground potential GND.Thus, it may be possible to suppress or prevent leakage of a magneticfield developed in the inductor L1 into the outside. Since the couplingbetween the inductor L1 and each nMOSQn, or the like, provided may besuppressed or prevented, the influence of external crosstalk may besuppressed or prevented. The other end of the inductor L1 may beelectrically connected to its corresponding upper electrode C1 a of thecapacitor C1 via a second layer wiring M24 (M).

A lower electrode C1 b may be provided in a wiring layer below the upperelectrode C1 a of the capacitor C1 so as to be opposite to the upperelectrode Cla with an insulating film interposed therebetween. The lowerelectrode C1 b may be electrically connected to its corresponding p⁺semiconductor region 11 c via a plug PL5. Further, the lower electrodeC1 b may be electrically connected to the low resistance p⁺ typesubstrate 1S via the p⁺ type semiconductor region 11 c. The outerperiphery of the capacitor C1 may also be surrounded by a first layerwiring M15, second layer wiring M25, plugs PL6 and p⁺⁺ typesemiconductor regions 11 d for shielding. The first layer wiring M15,the second layer wiring M25, the plugs PL6 and the p⁺⁺ typesemiconductor regions 11 d for the shielding may be electricallyconnected to one another (insulated from the capacitor C1). Further,they may be electrically connected to the low resistance substrate 1Svia the p⁺⁺ type semiconductor regions 11 d and may be set to the groundpotential GND. Thus, since the coupling between the capacitor C1 andeach nMOSQn or the like provided thereoutside may be suppressed orprevented, the influence of external crosstalk may be suppressed orprevented. Accordingly, the Q value of the capacitor C1 placed over thesubstrate 1S may be set high. The upper electrode C1 a of the capacitorC1 may be electrically connected to its corresponding gate electrode 8of the nMOSQn2 via a second layer wiring M26 (M). Incidentally, theplugs PL1 through PL6 may be respectively formed of a metal, such astungsten, or the like. Also, the fist layer wirings M11 through M15 andthe second layer wirings M21 through M26 may be respectively formed of ametal with, for example, aluminum (Al) or copper (Cu), as a main wiringmaterial. The p⁺⁺ type semiconductor regions 11 b through 11 d may beformed simultaneously upon the process of forming the p⁺⁺ typesemiconductor regions 11 a.

Next, FIG. 8 shows an overall plan view of an example of an RF powermodule PM in which the IC chip 1C may be mounted on a module board MCB.FIG. 9 is a cross-sectional view of a surface cut along the horizontaldirection of the power module PM shown in FIG. 8. FIG. 10 shows acircuit diagram of the power module shown in FIGS. 8 and 9.Incidentally, the chip mounting surface of the module board MCB is shownin FIG. 8 so as to be brought into sight with an encapsulating memberbeing eliminated therefrom.

The IC chip 1C may be mounted over a main surface of the module boardMCB in a state of being held in a recess called “cavity CBT” formed overthe main surface of the module board MCB in a state in which the backsurface of the substrate 1S may be being directed to the main surface ofthe module board MCB. The IC chip 1C may be placed slightly near theinput (left side in FIG. 8) as viewed from the center of the mainsurface of the module board MCB. A region on the output side of the mainsurface of the module board MCB may be wider than a region on the inputside thereof. Thus, since an output matching circuit placed in themodule board MCB of the RF power module PM may be designed to a lowloss, the output loss of the RF power module PM may be lessened andhence a high output may be fetched out.

Bonding pads Pin and Pout of the IC chip 1C are electrically connectedto transmission lines 15 a (15 a 1 through 15 a 5), 15 b (15 b 1 through15 b 5) and 15 c over the main surface of the module board MCB throughbonding wires BW. The transmission lines 15 a 1 and 15 b 1 connected viathe bonding wires BW to their corresponding gate electrodes (inputs) ofthe amplifying stages 2A1 and 2B1, corresponding to the first stage maybe electrically connected to their corresponding input terminals 17 aand 17 b via capacitors Cm1 and Cm2. The transmission lines 15 a 2 and15 b 2 electrically connected via the bonding wires BW to theircorresponding drains (outputs) of the amplifying stages 2A1 and 2B1,each corresponding to the first stage may be electrically connected totheir corresponding power supply terminals 18 a 1 and 18 b 1 on the highpotential side, and may be electrically connected to a ground potentialGND via capacitors Cm3 and Cm4 placed in the vicinity of the powersupply terminals 18 a 1 and 18 b 1. The transmission lines 15 a 3 and 15b 3 electrically connected via the bonding wires BW to theircorresponding drains (outputs) of the amplifying stages 2A2 and 2B2,each corresponding to the second stage may be electrically connected totheir corresponding power supply terminals 18 a 2 and 18 b 2 on the highpotential side and electrically connected to the ground potential GNDvia capacitors Cm5 and Cm6 disposed in the neighborhood of the powersupply terminals 18 a 2 and 18 b 2. The transmission lines 15 a 4 and 15b 4 electrically connected via the bonding wires BW to theircorresponding drains (outputs) of the amplifying stages 2A3 and 2B3 eachcorresponding to the final stage may be electrically connected to theircorresponding power supply terminals 18 a 3 and 18 b 3 on the highpotential side and electrically connected to the ground potential GNDvia capacitors Cm7 and Cm8 placed in the vicinity of the power supplyterminals 18 a 3 and 18 b 3. Further, the transmission lines 15 as and15 b 5 electrically connected via the bonding wires BW to theircorresponding drains (outputs) of the amplifying stages 2A3 and 2B3 eachcorresponding to the final stage may be electrically connected to theircorresponding output terminals 19 a and 19 b via capacitors Cm9 andCm10, and may be electrically connected to the ground potential GND viacapacitors Cm1 l and Cm12 placed in the middle of their lines. Thetransmission line 15 c electrically connected to its correspondingcontrol bonding pad Pin of the peripheral circuit 3 via a bonding wiremay be electrically connected to a control terminal 20. Incidentally,each of the bonding wires BW may be constituted of a thin line, such asgold (Au), and functions as an inductor. Also the transmission lines 15a and 15 b, respectively, may function as impedance matching inductors.The capacitors Cm1 through Cm12 may function as impedance matchingcapacitors and may be configured as chip parts.

On the other hand, the electrode 12 over the back surface of the IC chip1C may be bonded to a chip mounting electrode 21 at the bottom face ofthe cavity CBT of the module board MCB. Electrode 21 may be electricallyand thermally bonded to an electrode 23G over the back surf ace of themodule board MCB via conductors lying within a plurality of thermal vias22. The electrode 23G may be supplied with a reference potential (e.g.,ground potential GND, i.e., about 0V). That is, the reference potentialsupplied to the electrode 23G over the back surface of the module boardMCB may be supplied to the low resistance substrate 1S through thethermal vias 22 and the electrode 21. However, heat generated upon theoperation of the IC chip 1C may be transferred via the electrode 21 andthe thermal vias 22 from the back surface of the substrate 1S to theelectrode 23G placed over the back surface of the module board MCB, fromwhich the heat may be dissipated. Electrodes 23S located near the outerperiphery of the back surface of the module board MCB may indicatesignal electrodes. Incidentally, the module board MCB may have amulti-layered wiring structure formed by laminating a plurality ofinsulator plates and integrating them. Although the insulator plates maybe respectively made of ceramics, such as alumina (aluminum oxide: Al₂O₃and dielectric constant=9 to 9.7) low in dielectric loss up to, forexample, a millimeter wave region, the present invention is not limitedto it. Various changes may be made thereto and a glass epoxy resin orthe like may be used.

As seen in FIG. 11, an example of a digital cellular phone system DPSusing the RF power module PM according to the present invention isshown. Sign ANT in FIG. 11 may indicate a signal wavetransmitting/receiving antenna; reference numeral 25 may indicate afrontend module; reference numeral 26 may indicate the baseband circuit,which may convert a voice or audio signal to a baseband signal, mayconvert a receive signal to an audio signal and may generate amodulation scheme switching signal and a baseband switching signal;reference numeral 27 may indicate a modulator-demodulator, which maydown-convert the receive signal to demodulate it, thereby generating abaseband signal and may modulate a transmit signal; and FLT1 and FLT2may indicate filters which may eliminate noise and an interference wavefrom the receive signal, respectively. The filter FLT1 may be used forGSM and the filter FLT2 may be used for DCS. The baseband circuit 26 mayinclude of a plurality of semiconductor integrated circuits, such as aDSP (Digital Signal Processor), a microprocessor, a semiconductormemory, etc., for example. The frontend module 25 may include impedancematching circuits MN1 and MN2, low pass filters LPF1 and LPF2, switchcircuits 28 a and 28 b, capacitors C5 and C6 and a duplexer 29. Theimpedance matching circuits MN1 and MN2 may be circuits that areconnected to transmission output terminals of the RF power module PM toperform impedance matching. The low pass filters LPF1 and LPF2 may becircuits which attenuate higher harmonics; the switch circuits 28 a and28 b may be transmission/reception changeover switch circuits; thecapacitors C5 and C6 may be elements which cut dc components from thereceive signal, and the duplexer 29 may be a circuit which performbranching into a signal lying in the GSM900 band and a signal lying inthe DCS1800 band. These circuits and elements may be mounted on onewiring board so as to be configured as a module. Incidentally, select orchangeover signals CNT1 and CNT2 of the switch circuits 28 a and 28 bmay be supplied from the baseband circuit 26.

As seen in FIG. 12, a packaged example of the RF power module employedin the digital cellular phone system DPS shown in FIG. 11 is shown. Themotherboard 30 may comprise, for example, a printed wiring board, or thelike, having a multi-layered wiring structure. The RF power module PMand a plurality of chip parts 31 may be mounted over a main surface ofthe motherboard 30. The RF power module PM may be mounted over themotherboard 30 in a state in which the electrodes 23G and 23S, and thelike, placed over the back surface of the module board MCB may be beingdirected to the main surface of the motherboard 30. The electrodes 23Gand 23S, and the like, of the RF power module PM may be connected totheir corresponding wiring patterns of the motherboard 30 via jointingmaterials 32, such as solder, for example. Incidentally, the mainsurface of the mother board MCB of the RF power module PM may be coveredwith an encapsulating member 33 made of, for example, silicon rubber, orthe like. Thus, the IC chip 1C and the like placed over the main surfaceof the module board MCB may be sealed with the encapsulating member 33

In another exemplary embodiment of the present invention, ground bondingpads may be laid out among output bonding pads of adjacent amplifyingstages in the same system of an IC chip.

As seen in FIG. 13, one example of an overall plan view of the IC chip1C according to the present embodiment is shown. In the presentembodiment, ground bonding pads Pg may be disposed among output bondingpads Pout of a plurality of adjacent amplifying stages 2A1 through 2A3and 2B1 through 2B3 in respective power amplifier circuits 2A and 2Bprovided within the IC chip 1C. The ground bonding pads Pg may be padswhich supply a reference potential (e.g., ground potential GND: 0V) tothe IC chip 1C. Thus, since the feedback of a signal by emission from anext-stage amplifying element to a pre-stage amplifying element aftersignal amplification may be lessened, the suppression of oscillationsand stabilization of amplifying characteristics may be achieved.

As seen in FIG. 14, an overall plan view of one example in which the ICchip 1C shown in FIG. 13 may be mounted over a module board MCB toconfigure an RF power module PM is shown. A chip mounting surface of themodule board MCB may be shown so as to be brought into sight with anencapsulating member being eliminated therefrom. The ground bonding padsPg may be electrically connected to their corresponding ground terminals35 of the module board MCB through bonding wires BW. The referencepotential (e.g., ground potential GND: 0V) may be supplied to the groundterminals 35. Owing to the provision of such a configuration, powerradiated into space upon the operation of the RF power module PM may beabsorbed by the bonding wires BW each electrically connected to thebonding pad Pg and may be brought to the ground state, so that the powermay be greatly attenuated. Therefore, it may be possible to achievesuppression of oscillations and stabilization of amplifyingcharacteristics.

In yet another exemplary embodiment of the present invention, amodification illustrative of the layout of input and output bonding padsof adjacent amplifying stages in the same system of air IC chip may bemade.

As seen in FIG. 15, an overall plan view of the IC chip according to thepresent invention is shown. In an exemplary embodiment, input and outputbonding pads Pin and Pout of a plurality of adjacent amplifying stages2A1 through 2A3 and 2B1 through 2B3 may be laid out in respective poweramplifier circuits 2A and 2B lying within the IC chip 1C so as to bereversed by 180°. In the example shown in FIG. 15, the output bondingpads Pout of the amplifying stages 2A2 and 2B2, each corresponding to asecond stage, may be disposed near the center of the IC chip 1C, and theinput bonding pads Pin thereof may be laid out in the neighborhood ofthe sides of the IC chip 1C. In such a configuration, interstage wiringsM for connecting the input bonding pads Pin of the amplifying stages 2A1through 2A3 and 2B1 through 2B3 adjacent to one another and the outputbonding pads Pout thereof may extend substantially linearly withoutbending. In such a configuration, the interstage wirings M may beshortened, and the interstage wirings M and interstage matching circuits2AM2, 2AM3, 2BM2 and 2BM3 may be located away from the output bondingpads Pout of the next-stage amplifying stages as compared with exemplaryembodiments described herein. Therefore, it may be possible to reducecrosstalk from the next-stage amplifying stages to the interstagewirings M and the interstage matching circuits 2AM2, 2AM3, 2BM2 and2BM3. Thus, it may be possible to achieve suppression of oscillationsand stability of amplifying characteristics.

As seen in FIG. 16, an overall plan view of an aspect of the presentinvention is shown, in which the IC chip 1C shown in FIG. 15 may bemounted over a module board MCB to configure an RF power module PM. InFIG. 16, a chip mounting surface of the module board MCB may be shown soas to be brought into sight with an encapsulating member beingeliminated therefrom. Since the output bonding pads Pout of theamplifying stages 2A2 and 2B2, each corresponding to the second stagemay be placed near the center of the IC chip 1C in the presentembodiment as described above, the lengths of power supply bonding wiresBW for connecting the output bonding pads Pout of the amplifying stages2A2 and 2B2, each corresponding to the second stage, and power supplytransmission lines 15 a 3 and 15 b 3 of the module board MCB, may be setlonger than those of other bonding wires BW. Therefore, inductancecomponents for power lines to the amplifying stages 2A2 and 2B2, eachcorresponding to the second stage, may be increased by means of thebonding wires BW. Also, the lengths of the power supply transmissionlines 15 a 3 and 15 b 3 placed over the module board MCB may beshortened as compared with other exemplary embodiments described herein.Thus, a reduction in the overall size of the RF power module PM may bepromoted.

In another exemplary embodiment of the present invention, the layouts ofpower amplifier circuits in different systems of an IC chip may beopposite in direction to each other. As may be seen in FIG. 17, anoverall plan view of an IC chip 1C according to the present invention isshown. In the present exemplary embodiment, power amplifier circuits 2Aand 2B in different systems provided within an IC chip 1C may bedisposed so as to be opposite in input/output direction to each other.In particular, amplifying stages 2A3 and 2B3, each corresponding to afinal stage of the power amplifier circuits 2A and 2B of the differentsystems, may be disposed in the vicinity of diagonally-located ends ofthe IC chip 1C so as to be point-symmetric with each other. Thus, sincethe distance between the final amplifying stages 2A3 and 2B3 of thepower amplifier circuits 2A and 2B of the different systems may be madelong, crosstalk (emission or interference) from, for example, theoperated power amplifier circuit to the non-operated power amplifiercircuit, may be suppressed in a manner similar to previously describedexemplary embodiments, and the unnecessary occurrence of an output fromthe power amplifier circuit being in non-operation may be suppressed.Even if the power amplifier circuits 2A and 2B different in system areprovided in the same IC chip 1C, the crossband isolation characteristicbetween the power amplifier circuits 2A and 2B may be improved.

Although the exemplary embodiments described herein have explained thecase in which the present invention may be applied to the dual bandsystem capable of handling the radio waves lying in the two frequencybands of GSM900 and GSM1800, the present invention may also be appliedto a triple band system capable of handling radio waves lying in threefrequency bands of GSM900, GSM1800 and GSM1900, for example. Also, thepresent invention may additionally handle an 800 MHz band and an 850 MHzband.

Although the above description has principally been described as appliedto digital cellular phone systems, the present invention may also beapplied to, for example, a mobile information processing apparatus, suchas PDA (Personal Digital Assistants), or the like, having acommunication function and an information processing apparatus similarto a personal computer, or the like, having a communication function.Further, the semiconductor device according to the present invention maybe further applied to a semiconductor device having power amplifiercircuits of plural systems.

Those of ordinary skill in the art may recognize that many modificationsand variations of the present invention may be implemented withoutdeparting from the spirit or scope of the invention. Thus, it isintended that the present invention covers the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

1. A semiconductor device, comprising: a plurality of power amplifiercircuits configured in a multistage-connected form, wherein a first to afinal stage of the plurality of amplifier circuits are formed over onesemiconductor substrate of silicon, wherein the plurality of amplifiercircuits comprise field effect transistors, wherein drain and sourceelectrodes of the field effect transistors are respectively formed overa main surface and a back surface of the semiconductor substrate,wherein the respective source electrodes of the plurality of fieldeffect transistors are electrically connected to one another at the backsurface of the semiconductor substrate, wherein the respective sourceelectrodes are connected to a fixed potential, and wherein resistivityof the semiconductor substrate constituted of the silicon is less thanabout 5 mΩ·cm.
 2. A semiconductor device according to claim 1, whereinthe power amplifier circuits operate in one bandwidth of an 800 MHzband, a 900 MHz band, an 1800 MHz band and a 1900 MHz band.
 3. Asemiconductor device according to claim 1, wherein the semiconductorsubstrate is mounted over a wiring board, and the sources of the fieldeffect transistors are respectively electrically connected to a fixedpotential of the wiring board.
 4. A semiconductor device according toclaim 1, wherein the semiconductor substrate is provided with passiveelements for matching circuits.
 5. A semiconductor device according toclaim 4, wherein the semiconductor substrate is mounted over a wiringboard and provided with input and output matching circuits for each ofthe amplifier circuits.
 6. A semiconductor device according to claim 4,wherein shield layers are provided around the passive elements for thematching circuits, and wherein the shield layers are electricallyconnected to the semiconductor substrate through semiconductor regionsand electrically connected to a fixed potential via an electrode overthe back surface of the semiconductor substrate.
 7. A semiconductordevice according to claim 1, wherein the semiconductor substrate isprovided with a bias circuit and a control circuit used for theamplifier circuits.
 8. A semiconductor device according to claim 1,wherein a multiband system capable of coping with high frequency signalslying in a plurality of frequency bands is adopted for the semiconductordevice.
 9. A semiconductor device according to claim 1, wherein theamplifier circuits respectively comprise three amplifying stages.
 10. Asemiconductor device, comprising: first and second power amplifiercircuits differing in operating frequency, which respectively comprise aplurality of amplifier circuits configured in a multistage-connectedform; and passive elements for matching circuits employed in the firstand second power amplifier circuits and a bias circuit and a controlcircuit, wherein a first to a final stage of the plurality of amplifiercircuits of the first and second power amplifier circuits are formedover one silicon semiconductor substrate, wherein the plurality ofamplifier circuits respectively comprise field effect transistors,wherein drain and source electrodes of the field effect transistors arerespectively formed over a main surface and a back surface of thesemiconductor substrate, wherein the respective source electrodes of theplurality of field effect transistors are electrically connected to oneanother in the back surface of the semiconductor substrate, wherein thesource electrodes are respectively connected to a fixed potential, andwherein resistivity of the semiconductor substrate is equal to or lessthan about 10 mΩ·cm.
 11. A semiconductor device, comprising: a pluralityof amplifying stages each comprising amplifier circuits; and secondarycircuits, said all amplifying stages and said secondary circuits beingprovided over a same semiconductor chip, wherein the plurality ofamplifying stages are respectively formed of field effect transistorsplaced over a semiconductor substrate of silicon of the semiconductorchip, wherein the amplifier circuits are disposed on a periphery of amain surface of the semiconductor chip, and wherein the secondarycircuits are placed inside the periphery of the main surface of thesemiconductor chip.
 12. A semiconductor device according to claim 11,wherein resistivity of the semiconductor substrate is smaller than 10mΩ·cm, the field effect transistors are respectively configured ashorizontal type field effect transistors, and the sources of the fieldeffect transistors are electrically connected to the silicon substratethrough semiconductor regions and are electrically connected to a fixedpotential via an electrode over the back surface of the semiconductorsubstrate.
 13. A semiconductor device of a multiband system, which iscapable of coping with high frequency signals lying in a plurality ofdifferent frequency bands, said semiconductor device comprising: aplurality of amplifier circuits which respectively adapt to the highfrequency signals lying in the plurality of different frequency bands;and a plurality of amplifying stages which constitute the plurality ofamplifier circuits respectively, wherein each of the plurality ofamplifying stages are provided over one semiconductor chip, wherein theplurality of amplifying stages are respectively formed of field effecttransistors placed over a semiconductor substrate formed of silicon ofthe semiconductor chip, and wherein the amplifying stages correspondingto a final stage of the plurality of amplifier circuits are placed atsides of the semiconductor chip opposite to each other.
 14. Asemiconductor device according to claim 13, wherein the final amplifyingstages of the respective amplifier circuits are disposed to bepoint-symmetric to each other.
 15. A semiconductor device according toclaim 13, wherein resistivity of the semiconductor substrate is lessthan 10 mΩ·cm, the field effect transistors are respectively configuredas horizontal type field effect transistors, and the sources of thefield effect transistors are electrically connected to the semiconductorsubstrate through semiconductor regions and are electrically connectedto a fixed potential via an electrode over the back surface of thesemiconductor substrate, and wherein the semiconductor chip is providedwith passive elements for matching circuits, and a bias circuit and acontrol circuit for the amplifier circuits.
 16. A semiconductor deviceaccording to claim 14, wherein the plurality of amplifier circuitsrespectively include three amplifying stages.
 17. A semiconductordevice, comprising a plurality of amplifying stages constitutingamplifier circuits, said amplifying stages being provided over asemiconductor chip, wherein the plurality of amplifying stages arerespectively formed of field effect transistors placed over asemiconductor substrate constituted of silicon of the semiconductorchip, and wherein electrodes electrically connected to a fixed potentialare disposed between at least two of the plurality of amplifying stages.18. A semiconductor device according to claim 17, wherein resistivity ofthe semiconductor substrate is smaller than 10 mΩ·cm, the field effecttransistors are respectively configured as horizontal type field effecttransistors, and the sources of the field effect transistors areelectrically connected to the semiconductor substrate throughsemiconductor regions and are electrically connected to a fixedpotential via an electrode over the back surface of the semiconductorsubstrate.
 19. A semiconductor device, comprising: a plurality ofamplifying stageshaving amplifier circuits respectively, said amplifyingstages being provided over the same semiconductor chip, wherein theplurality of amplifying stages are respectively formed of field effecttransistors placed over a semiconductor substrate constituted of siliconof the semiconductor chip, and wherein the plurality of amplifyingstages are disposed to provide input and output units of the respective,adjacent ones of the amplifying stages respectively opposed.
 20. Asemiconductor device according to claim 19, wherein resistivity of thesemiconductor substrate is smaller than 10 mΩ-cm, the field effecttransistors are respectively configured as horizontal type field effecttransistors, and the sources of the field effect transistors areelectrically connected to the semiconductor substrate throughsemiconductor regions and are electrically connected to a fixedpotential via an electrode on a back surface of the semiconductorsubstrate.
 21. A semiconductor device suitable for mounting in acellular phone, comprising: power amplifier circuits, wherein the poweramplifier circuits comprise a plurality of amplifier circuitsconstituted of field effect transistors configured in amultistage-connected form, wherein the respective power amplifiercircuits are connected to one another via impedance matching circuitscomprising passive elements, wherein the power amplifier circuits arecontrolled by a control circuit, and wherein the amplifying circuitsconstituting the power amplifier circuits are formed over a singlesemiconductor substrate formed of silicon.
 22. A semiconductor device,comprising: a first power amplifier circuit formed over a firstsemiconductor chip and comprising a plurality of amplifier circuitsconfigured in a multistage-connected form; and a wiring board having thefirst semiconductor chip paged thereover, wherein the firstsemiconductor chip has a semiconductor substrate formed of silicon,wherein the plurality of amplifying circuits comprise field effecttransistors formed in the semiconductor substrate, and wherein asemiconductor chip including the power amplifier circuits and mountedover the wiring board is present exclusively on the first semiconductorchip.
 23. A semiconductor device according to claim 22, wherein drainand source electrodes of a plurality of the field effect transistorsconstituting the plurality of amplifier circuits are respectively formedover a main surface and a back surface of the semiconductor substrate,wherein the respective source electrodes of the plurality of fieldeffect transistors are electrically connected to one another at the backsurface of the semiconductor substrate, wherein the source electrodesare connected to a fixed potential, and wherein resistivity of thesemiconductor substrate is smaller than 10 mΩ·cm.
 24. A semiconductordevice according to claim 22, wherein the plurality of amplifiercircuits have systems operated in different frequency bands.
 25. Asemiconductor device according to claim 22, wherein the first poweramplifier circuit operates in one of an 800 MHz band, a 900 MHz band, a1800 MHz band and a 1900 MHz band.